This invention relates to a method to determine filter pluggage.
It is known to produce nonwoven fabrics by jetting liquid streams into a layer of fibrous material to entangle the fibers. Liquid is jetted at high pressure from a line of orifices in a jet to form high energy streams. The energy of the stream is proportional to the pressure at which the stream is formed and to the volumetric flow rate. To protect the orifices in the jet from particles in the liquid that may plug the orifices, it is known to install a filter in the liquid supply upstream of the orifices. As the filter removes particles from the liquid, the pressure drop across the filter increases. If the pressure drop exceeds a specified limit, the filter may self-destruct or, in the alternative, the pressure at the jet orifices may be reduced resulting in loss of flow through the orifices which in turn has a deleterious effect in the form of a loss of strength of the non-woven product being formed.
One way to insure that the filters do not fail is to change them on a time basis. However, it has been found that when filters are changed on a time basis, most of the filters had not reached their full life cycle resulting in an ineffective costly operation.
Another way to monitor the condition of the filter is to install a differential pressure transmitter across the filter to signal an alarm when the filter pressure builds up due to blockage beyond a specified limit. This requires the costly installation of transmitters and electronic equipment.